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High Frequency Noise
High frequency noise is primarily created by our
increased use of modern electronic equipment. This is
usually very localized and has not been proven to have
any human health effects.
Key Facts
• MREC member utilities' electrical systems deliver energy to
our customers using a 60 cycle per second alternating
current.
• Our customers' normal electric power use can sometimes
cause changes to the normal 60 cycle per second current flow.
These changes may take the form of very short duration
transients, or very slow voltage variations that may be noticed
as lights flickering.
• The increasing use of modern technological devices,
including radios, computers, cell phones and microwaves
results in the presence of high frequency electrical currents
on the wiring of our homes and businesses.
• High frequency electrical noise is almost always created in
the customer's home or workplace wiring, and cannot easily
be transmitted across the high voltage transmission system.
• High frequency noise may interfere with radio or television
reception and possibly the operation of some electricpowered equipment, but at normal levels of exposure there
are no proven health effects from high frequency noise .
Questions and Answers
Our modern electrical system uses alternating electrical
current that cycles 60 times per second to transmit energy
from the generating plant to the customer. This 60 cycle (or
Hertz, Hz) power appears as a smooth alternating wave on
an oscilloscope, a special instrument capable of measuring
power waveforms and other electrical signals such as those
from radios, televisions and cell phones. This smooth 60 Hz
wave is created by utility generating systems and is
transmitted across both the regional transmission and local
electrical distribution systems to our homes, businesses and
farms.
.
What are electrical transients?
Occasionally, there may be short duration changes to voltage
or current levels that are transmitted across the electric grid
due to switching occurring within the grid , sudden changes in
customer loads, lightning or temporary faults. These are
called transients. Customers may notice transients as a quick
flickering of the lights across a wide area. Local transients
can also be caused by events that take place in your wi ring
system such as a motor starting or a light turning on. While
the laws of physics governing the flow of electricity allow the
passing of 60 Hz waves within the distribution system, these
same laws limit the movement of faster moving (shorter
duration) transients. As a result, customer loads generate the
majority of transients that can be measured in the wiring
systems of homes and businesses.
What is high frequency noise?
Like short duration transients, high frequency noise is not
something generally transmitted over the power system to our
customers. The sources of system noise are found primarily
in the electrical equipment we use in our homes and
businesses. An operating electric motor, for example, will
distort an otherwise smooth 60 Hz waveform by adding to it
tiny high frequency electrical signals or "noise." This high
frequency noise is almost always much smaller than the
supply voltage (120 volts) and can only be detected with
sensitive measurement equipment. Although normally very
small, high frequency noise can cause problems for some
electronic equipment. A good example of this phenomena is
the "snow" that you see on your television when someone
nearby operates an electric hair dryer or a vacuum cleaner.
These devices put noise on the building wiring system, and
the television, operated from the same wiring, is adversely
affected by the noise. High frequency signals from television
and radio stations can also radiate into your wiring because
your wiring can act as an inefficient antennae. In the past few
years, there has been more discussion about the presence of
this localized high frequency noise and perceived health
effects.
What is the consequence of this high frequency noise?
As we have all seen on our television screens or heard on
our AM radios, these high frequency signals can be
detected and can interfere with radio and television
reception, and possibly cause the miss-operation of other
equipment.
Are there any health effects of high frequency noise?
No medical research links localized high frequency noise,
the kind we encounter during the normal course of our
lives, with any health effects. Consequently, claims linking
high frequency noise with a variety of illnesses ranging
from anxiety attacks to chronic fatigue syndrome are
unprove n.
Can I buy any devices that remove high frequency
noise?
MREC member utilities are aware of equipment that claims
to remove high frequency noise or to “send it back” to the
utility. Unfortunately, these devices do not eliminate the
source of the high frequency signal, and the laws of
physics do not allow a high frequency signal generated by
customer equipment to be transmitted back to MREC
utilities. More importantly, use of these devices may create
unsafe conditions if they have not been approved for use by
an independent testing agency such as Underwriter's
Laboratory (UL). MREC member utilities do not offer any
devices for sale, nor do we endorse any product or its use .
What are MREC member utilities doing about high
frequency noise?
First, we are attempting to educate our customers about
the source of high frequency noise. We are also supporting
research to increase our understanding of its causes and
how to minimize its potential effect on sensitive electronic
equipment. MREC member utilities continue to support
research for improving the efficiency and maintaining the
safety of our distribution system. All electric distribution
system upgrades follow both Public Service Commission of
Wisconsin and National Electrical Safety Code
requirements. Finally, we provide guidance to customers
who have questions or concerns about transients and high
frequency noise .
How can I obtain more information?
If you have specific questions about high frequency noise,
contact your electric utilities directly or visit our website at
www.mrec.org .
What is the MREC?
The MREC is a membership organization of energy
suppliers, energy service professionals and Land Grant
Universities whose mission is to support outreach,
education and research on rural energy issues for the
benefit of:
• Farms and other rural energy consumers
• Rural energy suppliers
• Farm organizations and agricultural trade associations
• Electrical equipment and allied industries
• Government and regulatory agencies